1. Field of the Invention
The invention relates in general to transportation apparatus, such as escalators and moving walks, and more specifically to transportation apparatus having an electrically controlled brake.
2. Description of the Prior Art
My U.S. Pat. No. 4,600,865, entitled Transportation Apparatus, which issued July 15, 1986, describes and claims transportation apparatus in which deceleration is directly controlled when such apparatus is stopped. The direct control of deceleration includes a deceleration servo loop which provides a current signal for an inner current loop which regulates brake current to cause the transportation apparatus to stop at a predetermined constant deceleration rate. In one embodiment of the invention set forth in my U.S. patent, the running brake current, i.e., the brake current prior to the initiation of a controlled stop, is also included in the servo loop, and regulated to a predetermined constant value. It was felt that by regulating the running brake current to a constant value, the brake would always be fully lifted when the transportation apparatus was in its normal running mode, compensating for brakes which were sensitive to brake temperature and supply voltage variations.
Actual experience with an escalator having an electrically controlled brake constructed as set forth in my U.S. patent has proven that partial setting of the brake can still occur during normal running conditions, notwithstanding regulating the brake running current to a constant value.